1. Field of the Invention
This invention relates broadly to the manufacture of filtering apparatus. In particular, it relates to a unique method of sealingly coupling the end of a potted hollow fiber filter bundle to a module casing and the unique collar device used in conjunction therewith.
2. Description of the Related Art
Hollow fiber filter modules are known in the art. Typically, a hollow fiber filter module is comprised of a plurality of porous elongated hollow fibers having an inner diameter of about 100.mu. to 1000.mu., packed at a specific density within a casing. Conventional hollow fiber permeability apparatus are used extensively in the medical field, for example in hemodialysis and in artificial lungs. Hollow fiber membrane filters are also extensively used in the purification and desalination of water commonly known as reverse osmosis filtering apparatus.
Porous, hollow fibers are used in a wide variety of permeability and filter applications because of a basic advantage over flat membranes. Available surface area is increased by choosing porous, hollow fibers thereby reducing space requirements for permeability apparatus. The hollow fiber membrane filters, therefore, provide effective filtration of a large variety of different fluids at-an elevated flow rate because of the high density of surface area available for filtration.
The generally accepted method of manufacturing hollow fiber filter modules is to retain a rectilinear bundle of hollow fibers within a casing, immerse the longitudinal distal ends of the hollow fiber bundle in a potting compound which will adhere, at least temporarily, to the casing. The potting compound abuts the inner surface of the casing and occupies the interstitial void between the individual fibers thus preventing contaminated liquid from coming into contact with the filtrate. Depending on the application, a cross-sectional portion of the potting compound from one or both longitudinal ends of the potted fiber bundle is removed thus providing access to the lumen of the individual hollow fibers.
A difficulty commonly encountered in the construction of the hollow fiber filter modules is the frequent failure of the potting compound to sealingly bond to the casing and in particular the frequent loss of sealing engagement between the potting compound and the casing after autoclaving of the hollow fiber filter module. This results in the leakage of contaminated fluid into the filtrate. Thus, once or twice autoclaved the module must be discarded. This practice is costly to industries that rely on filtered fluids such as the semi-conductor, pharmaceutical, biotechnology, and medical research industries. In addition, repeatedly discarding large numbers of non-biodegradable modules out of necessity because reuse is limited is environmentally unsound.
Attempts to correct the aforementioned problems have met with limited success. For instance, attempts have been made to seal the junction of the potting component and the module with an O-ring sandwiched between the module and the distal end of the potting compound. However, this was largely unsuccessful because an O-ring is not suited for use as a primary seal. Rather, an O-ring is best suited for use as a secondary seal with the contacting surface of the module and the distal end of the potting compound functioning as the primary seal.
Accordingly, a substantial need exists for a hollow fiber filter cartridge that has a high integrity seal between the potting compound and the casing whereby leakage of contaminated fluid into the filtrate stream is prevented. A further need exists for a hollow fiber filter cartridge that can be autoclaved numerous times thus making the multiple reuse of filter cartridges practical and feasible.